Process of manufacturing mercapto-benzo-thiazole



Patented 1...... 7, 1927.

UNITED STATES PATENT OFFICE.

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PROCESS OI IAHUI'AGTUBIHG WO-BENZO-TEIAZOLR.

Ho Drawing.

My invention'relates to a method of producing an accelerator and it isparticularly directed to the manufacture of mercaptobenzothiazole, whichhas been found to be a 5 highly ellicient accelerator.

It has been suggested, heretofore, that mercaptobenzothiazole beutilized as an accelerator, and a method of its production has beensuggested which, however, unnecessarily increased the cost thereof.Although the accelerator, even as prepared heretofore, is not anexpensive chemical, nevertheless its cost may be materially reducedbyifollowing the method of my invention. eretofore,

the production of the accelerator was accomplished by first producingthiocarbanilid, which I have discovered is an unnecessary step in theproduction of the chemical.

In addition to decreasmg the expense of producing mercaptobenzothiazole,my invention prevents the formation of anilidobenzothiazole, which isformed in the usual process of manufacturing the above designatedmaterial. It is believed that anilido- 2 benzothiazole tends to softenthe rubber stock when it is compounded therewith along with theaccelerator andmay possibly retard acceleration of the vulcanization toa certain extent. In any event, its presence 1s not desirable and bypracticing the method of my invention its formation is prevented.

A further advantage of my invention resides in the fact that a muchhigher yield of mercaptobenzothiazole may be obtained from the materialsnecessary to its formatio which aids materially in reducing the cost 0the ultimate product. Heretofore, yields of approximately 50% wereprobably the highest obtainable, whereas with my process a yield of 95%of mercaptobenzothiazole may readily be obtained without any expensiveequipment, or without exercising .unusual care in its production.

In practicing my invention, I utilize a pri- 4 mary amine and sulfur,which reagents are associated with carbon bisulfide in excess of theamount of the first mentioned chemicals. With such a mixture, oragglomeration, of materials disposed in a suitable vessel such,

for example, as an autoclave, heat is applied to produce a temperatureof at least 150 C. U on the application of the heat hydrogen sulfide .isgenerated which, if not permitted to escape, gradually increases thepresure Application fled August 7, 1888. Serial Io. 580,318.

in the autoclave. I have found that it is desirable to regulate thepressure obtained in the autoclave, and this may readily be done bymerely fitting a conduit thereto supplied with a suitable valve ofordinary type. For the best conditions to obtain a high yield ofmercaptobenzothiazole, atemperature of substantially 250 to 300 C. maybe utilized conditions set forth are only given to illus-' trate therange of temperatures and pressures which are desirable forexceptionally high yields. 'If an amine, sulfur, and carbon bisulfideare merely disposed in an autoclave and heat applied so that atemperature of about 280 to 285 C. is established, the pressure willincrease to between 600 to 700 pounds per square inch. The production ofmercaptobenzothiazole under such conditions will be from 95 to 97% ofthe theoretical, but if the pressure is released at 250 pounds, by meansof a suitable valve, and maintained at that amount, the yield will beapproximately 75%. It is apparent, therefore, that the yield varies withthe pressure established, but it is not necessary to regulate thepressure to a very great extent in order to obtain high yields. Forexample at a temperature of 250 C. a pressure of 450 pounds isdesirable, but it may vary more than 100 pounds in either directionwithout affecting the yield materially.

The product resulting from the reaction of the amine, sulfur" and carbonbisulfide heated in the autoclave under a regulated ressure, isdissolved in sodium hydroxide mm which solution the puremercaptobenzothiazole or one of its homologs is precipitated 'by theaddition of an acid, such as hydrochloric. The resulting material isthen filtered, washed and dried, the final product being commerciallypure mercaptobenzothiazole, which is highly eflicient in theacceleration of the vulcanization of rubber and rubber compounds. I

If aniline and carbon bisulfide are associated in the presence of sulfurat ordmary temperatures, thiocarbanilid is formed and hydrogen sulfideis evolved. With other amines analogous reactions occur. If hydro gensulfide is brought into intimate association with a thiourea at about140 (3., \t is completely decomposed into amine and carbon bisulfideeven at atmospheric pressure.

Consequently, it will be readily understood that the hydrogen sulfideprevents the formation of thioc'arbanilid at high pressures. Thepressure of the hydrogen sulfide on the other hand is insuflicient toprevent the OK!- dation of the ortho H atom of the benzol rin and thesubsequent splitting off of the hy rogen sulfide to close the thiazolring. The hydrogen sulfide, however, will prevent the oxidation of themercaptan to the disulfide, and, consequently, a reaction is Obs tainedwhich is forced to follow a given course and thus results in nearlytheoretical yields. With other amines, such, for example, as ortho andpara toluidine, the yields are less because of side reactions involvingthe methyl (CH group.

Althou h I have specifically described a process 0 producingmercaptobenzothiazole and given specific temperature and pressureconditions suitable for reducing production costs, it is obvious thatminor changes may be made in the conditions established in the processand in the exact manner of establishmg such conditions without departingfrom the spirit or scope of the invention, andI desire, therefore, thatno limitations shall be imposed except such as are indicated in theappended claims.

What I claim is:

1. A method of producing mercaptothiazoles or their homologs thatcomprises associating a primary aromatic amine having a free orthoposition with sulphur and carbon bisulfide, subjecting the mixture to atemperature between 150 C. and 300 C. and establishing a pressure of atleast 100 pounds per square inch.

2. A method of producing mercaptodines, xylindines, anisidines, aromaticdiamines, etc.,

The following equations indicate the reactions that occur w ien one mol.(93 grs.) of aniline is used with one mol. (32 grs.) of sulfur and onemol. (76 grs.) plus 15% to 20% excess of carbon bisulfidMemptobenzothlazole.

thiazoles or their homologs that comprises associating a primaryaromatic amine having a free ortho position with sulfur andsubstantially 15% to 20% greater quantity of carbon bisulfide, andsubjecting the materials to a temperature between 150 C. and 300 C. anda pressure of not less than 100 pounds per square inch.

3. A method of producing mercaptobenzothiazole that comprisesassociating aniline with sulphur and carbon bisulfide at a temperaturebetween 150 C. and 300 C, and under a pressure between 100 and 700pounds per square inch.

4. A method of producing mercaptobenzothiazole that comprisesassociating aniline with sulphur and carbon bisulfide at a temperatureof substantially 250 C. and under a pressure of approximately 450 poundsper square inch.

5: A method of producing mercaptobenzothiazole or its homologs thatcomprises associating a primary phenyl amine having a free orthoposition with sulfur and carbon bisulfide, subjecting the materials to atemperature between 150 C. and 300 C., and maintaining a positivepressure, regw lated by permitting the escape of the gas generated.

6. A method of producing a mecaptothiazole that comprises associating aprimary aromatic amine having a free ortho position with sulfur and aquantity of caron bisulfide 15% to 20% greater than the first mentionedmaterials, applying heat thereto in order to produce a temperature ofsubstantially 250 C., and regulating the pressure by controlling theescape of generated gas to maintain approximately 450 pounds per squareinch upon the materials.

7. A method of producing a mercaptobenzothiazole that comprisesassociating a primary phenyl amine having a free ortho position withsulfur and carbon bisulfide, subjecting the materials to a temperaturebetween 150 C. and 300 0., regulating the pressure by controlling theescape of gas generated, dissolving the product in sodium hydroxide,preci itatin the merca toben-- zothiazole by ad ing acld, filtering t eprecipitate, washing and drying the product.

8. A method of producing mercaptobenzothiazole that comprises mixing onemol. of aniline with one mol. of sulfurcand one mol. plus 15% to excessof carbon bisulfide, applying heat thereto to establish a temperature ofsubstantially 250 0., and regulating the pressure by controlling theescape of generated gas to maintain approximately 450 pounds per squareinch upon the materials. I

9. A method of producing mercaptobenzothiazole or its homologs thatcomprises confining the corresponding primary aromatic amine havinganavailable ortho position with sulfur and carbon bisulfide in acontainer and applying heat to create a temperature of 150 to 300 C.

10. A method of producing thiazoles which comprises causing a primaryaromatic amine having an available ortho position to react with sulfurand carbon bisulfide under positive pressure and elevated temperaturenot to exceed the decomposing.

temperature of the product 'mary aromatic amino having an availableortho pbsition to react with sulfur and car- .bon bisulfide underpositive pressure and at a temperature of not less than 150 C. and notmore than the decomposing temperature of the product.

12. A method of producing mercaptoarylthiazoles that comprisesassociating a corresponding primary aromatic amine having an availableortho position with sulfur and carbon bisulfide under positive pressureand elevating temperatures not to exceed the decomposing point of theproduct.

a 13. That step in thev manufacture of thiazoles which consists insubjectin the reaction product of sulphur, carbon iisulfide and aprimary aromatic amine having an available ortho position to a positivepressure of hydrogen sulfide and an elevated temperature not to exceedthe decomposition temperature of the thiazole product.

In witness whereof, I have hereunto signed my name.

WILLIAM J. KELLY.

